Electrostatic device for holding an electronic component wafer

ABSTRACT

A device for holding a wafer, an electronic component comprises a system for transporting without deformation a wafer of electronic components. The device also enables the transport by one or the other of the passive or active faces. The device comprises a planar and thin rigid support having a controllable temperature and at least an electrode consisting of (N+1) elements, confined between two sheets of insulating material. The support provides a protrusion-free surface for gripping the wafer, and electrostatic elements for positive retention of the wafer induces a gripping power of the latter distributed over the entire support. The U-shaped support is borne by the electrical bond of the electrode with a remote (adjustable, AC or DC, mono-multipolar) power source. The gripping surface of the device is planar and protrusion-free whatever the geometry of the support used.

[0001] The invention is in the field of the technique of manipulatingsheet material, more particularly wafers of micrometric electroniccomponents, such as silicon. The invention has for its object a devicefor holding such material, a so-called wafer.

[0002] It will be recalled, in the field of electronic components, thatsheet-like elements called wafers are used, such as of silicon. Theproblem arises for holding such slices because of their slightthickness. More particularly, the thin character of these wafers, of theorder of several tens to several hundreds of microns, renders theirholding delicate with the risk of deforming them, even altering thecomponents that they support. At present, these wafers are manipulatedby means of their passive surface, to avoid alteration of their otheractive surface, which supports electronic components.

[0003] There is known a technique of holding wafers by suction. Forexample, the wafer is pressed by its passive surface against a flatsurface of a suction cup of a pipette which transmits suction. However,the development of techniques tends to make the wafers even thinner,which renders more and more sensitive their holding, even renderingtheir manipulation impossible by suction in the above manner. Moreover,because of being able to hold the wafer only by its passive surface,operative constraints are imposed on the technique of manipulating thewafer.

[0004] The object of the present invention is to provide a device forholding a wafer for supporting particularly electronic components or thelike, which permits their manipulation without damage or deformation,and without risk of altering the electronic components that they carry.Another object is to provide such a holding device, which permitsholding a wafer, either by its passive surface or by its active surface,to increase the operative possibilities for its manipulation.

[0005] The device of the present invention is of the type of devicecomprising a holding member for the wafer, particularly for support,provided with positive means for holding the latter against an overallflat surface of the holding member.

[0006] The inventive concept of the present invention consists inproviding an electrostatic device for holding a wafer, comprising a flatand thin rigid support, which constitutes the above mentioned holdingmember. At least one electrode, which constitutes the positive holdingmeans for the wafer, is connected to one of the surfaces of the flatsupport, which is provided to be the carrying surface for the wafer.

[0007] This device is a transport system without deformation of a waferfor electronic components or the like. The device also permits thistransport by one or the other of the passive or active surfaces of thewafer.

[0008] These arrangements are such that the support offers a holdingsurface for the wafer which is free from protuberances likely to alterit. Moreover, the positive support means for the wafer has an adjustableholding power for this latter which is distributed over all thecorresponding surface of the support. As a result, not only is there ahomogeneous distribution of the holding forces on the wafer, which tendsto protect it from stress points, but also a better holding of thislatter.

[0009] Thanks to these arrangements, a wafer, even of very smallthickness such as the order of ten microns, can be held without risk ofbeing altered or deformed by the power source for the positive holdingmeans. Moreover, the device of the invention renders possible holding ofthe slice by its active surface, not withstanding the presence ofcomponents, without the risk of altering or damaging these latter.

[0010] It will be understood that the electrode, particularly of copperor the like, understood as delimited by its surface of superposition tothe corresponding surface of the support, is associated with remotesupply means for electrical energy, to which it is connectable by meansof connection members with which it is provided.

[0011] The support is itself preferably of rigid material, insulating orconductive, so as to offer a suitable rigidity without at the same timehaving an undesirably increased thickness. This thermostatic supportmoreover has the property of adjusting and controlling the temperature.

[0012] The electrode is preferably confined between two sheets ofinsulating material, particularly Kapton (trademark) or any otherdielectric material, which is to say particularly with the exception ofat least one access window to its connection members. These arrangementsseek to protect the electrode, both as to its contact with the supportand as to the external environment.

[0013] For holding particularly a wafer of disc shape, at least oneelectrode, if not also and preferably the support, is of overall U shapeor the like. Each of the legs of this U corresponds to a branch of theelectrode. The base of the U is preferably prolonged by two connectiontongues associated each with a respective branch of the electrode. Itwill however be understood that the shape of the electrode and thearrangement of it and its branches, is particularly determined accordingto the configuration of the wafer to be supported, so as best todistribute to the surface of this latter the power of the positiveholding means.

[0014] It follows that any other geometric shape of the support and/orof the electrode is permissible without thereby departing from the scopeof the invention.

[0015] According to a preferred embodiment, the device of the inventionis completed by a member for holding the support, such as an arm, forits manipulation. It will be noted that this manipulation can be asdesired a manual manipulation or an automated manipulation. This holdingmember of the support comprises securement means for the support, suchas by riveting the temperature control members, and members to conveyelectrical energy as well as the control of the presence of a wafer onthe support from the remote source to the electrode, which areconnectable to the connection members of the electrode, through theabove mentioned window for example.

[0016] The present invention will be understood and the relevant detailswill appear from the description which follows of a preferred embodimentof the invention, with respect to the figures of the accompanyingdrawing, in which:

[0017]FIG. 1 is an exploded perspective view of a device according to apreferred embodiment of the invention.

[0018]FIGS. 2 and 3 are perspective views of a device shown in FIG. 1,assembled, which is fixed to a manipulation arm, these views beingrespectively exploded and assembled views of this securement.

[0019] In the drawings, a device according to the invention for holdinga wafer 2, is a layered device comprising successively:

[0020] a) a rigid flat support 4, of stainless steel particularly, or ofa ceramic insulating material or the like,

[0021] b) a first layer of insulating material 6, such as Kapton or anyother dielectric material,

[0022] c) an electrode 8, of copper or the like,

[0023] d) a second layer of insulating material 10, such as Kapton.

[0024] The first layer of Kapton is cemented to the support 4; theelectrode is held between the two layers of Kapton 6-10 and the layer 10of insulating material is, during holding, in contact with the wafer tobe manipulated.

[0025] The particular U shaped configuration of the support 4 and of theelectrode 8 which it carries, will be noted. Each leg of the Ucorresponds to a respective branch 12 and 14 of the electrode, prolongedby connection members 16 and 18 of the electrode to a remote source 20for the support of electricity.

[0026] The support 4 can have any geometric shape suitable to obtaingood holding of the wafer.

[0027] The electrode has a shape which is adapted to that of the supportas well as the insulating sheets.

[0028] The support 6 is fixed by rivets 22 to the end of a holding arm24. This arm 24 comprises members 26 and 28 for electrical connectionbetween the electrode 8 and the remote supply source 20. It will benoted that the upper insulating layer 10 covering the electrode 8comprises access windows, such as 30, to the connection members of thislatter. These windows 30 are provided to permit contact between theconnection members 16, 18 of the electrode 8, and the correspondingelectrical connection members 26 and 28 which comprise the arm 24.

[0029] There will be noted several appropriate characteristics of thedevice of the invention given by way of example. Particularly as to thesupport 4, the stainless steel used is of the type called 316L, to bethe thinnest possible with sufficient rigidity. Moreover, a flatness ofthe support 4 of the order of 0.01% is desirable. The assembly comprisedby the electrode 8 and the sheets 6 and 10 of insulating material is ofthe order of 110 μM, plus or minus 10 μm. The insulating films 6 and 10of Kapton guarantee electrical insulation greater than 2000 Vdc onopposite sides of the electrode 8. For this purpose each has a samethickness of the order of 50 μm. The electrode 8 itself is formed from asheet of copper of a thickness of the order of 10 μm or any otherelectrically conductive material.

1. Device for holding a wafer (2) of an electronic component or thelike, of the type comprising a holding member for the wafer (2),provided with positive holding means for this latter pressed against anoverall flat surface of the holding member, characterized: as anelectrostatic holding device for the wafer (2), it comprises a rigidflat support (4), thin and temperature controlled, which constitutes theholding member, and at least one electrode (8), which constitutes thepositive holding means of the wafer (2), such that the support (4)offers a holding surface for the wafer (2) free from irregularities andthat the positive holding means (8) for the wafer (2) has a holdingpower for this latter (2) distributed over all the support (4). 2.Device according to claim 1, characterized: in that the electrode (8) isassociated with remote electrical energy supply means (20) to which itis connectable by means of connection members (16, 18) with which it isprovided, and is associated with one of the surfaces of the support (4).3. Device according to any one of the preceding claims, characterized inthat the support (4) is of stainless steel.
 4. Device according to anyone of the preceding claims, characterized in that the electrode (8) isconfined between two sheets (6, 10) of an insulating material.
 5. Deviceaccording to claim 4, characterized: in that the insulating material isKapton, of which each of the sheets (6, 10) has a thickness of the orderof 50 μm, for an electrical insulation greater than 2000 Vdc on oppositesides of the electrode (8).
 6. Device according to any one of thepreceding claims, characterized: in that the electrode (8) is formedfrom a sheet of copper of a thickness of the order of 10 μm.
 7. Deviceaccording to any one of the preceding claims, characterized: in that atleast one electrode (8), if not also the support (4), is overall of Ushape, of which each of the branches corresponds to a branch (12, 14) ofthe electrode (8), and whose base is prolonged by two connection tongues(16, 18) associated each with a respective branch (12, 14) of theelectrode (8).
 8. Device according to any one of the preceding claims,characterized: in that it moreover comprises a member (24) for holdingthe support for its manipulation, which comprises securement means (22)for the support (4), and members (26, 28) connectable to the connectionmembers (16, 18) of the electrode (8) to supply electrical energy from aremote source (20) to the electrode (8).